1. Field of the Invention
The present invention relates to a take-up machine of a wire coating line, particularly to a traveling wire take-up method and its method capable of reducing failures of changeover from a bobbin presently (currently) taking up a traveling wire to an empty bobbin.
2. Description of Related Art
First of all, a generic construction of a wire coating line is explained by taking an example of a tandem insulating coating line of FIG. 5. The wire coating line includes a wire drawing machine 1, an annealing machine 2, an extruding machine 3, a cooling trough 4, a capstan 5, a dancer roller 6, and a take-up machine 7 being disposed in this order. In the drawing, a reference numeral 8 denotes a control board.
A copper wire drawn to be a predetermined radius in the drawing machine 1 is heated in the annealing machine 2 so as to remove work hardening and, in turn, is preliminary heated at a predetermined temperature. Then, in the extruding machine 3, an insulating coating such as a solid polyethylene is applied on the preheated copper wire. And, this coating layer is cooled down by cooling water in the cooling trough 4 and, subsequently, driven by the capstan 5 at a predetermined speed. This capstan 5 determines a traveling speed of the traveling wire 9. The traveling speed can be increased up to 2000-2500 m/min. Further, this traveling wire 9 is taken up by the take-up machine 7 via the dancer roller 6. This dancer roller 6 comprises a fixed sheave and a movable sheave. By detecting a position of the movable sheave, a rotational speed of the bobbin is controlled to be reduced in accordance with a winding thichness of the presently taking up bobbin in the take-up machine 7.
Moreover, the movable sheave is driven by a torque motor so as to provide the traveling wire 9 reaching the take-up machine 7 with a predetermined tension. The take-up machine 7 comprises a presently take-up bobbin and an empty bobbin, so that the bobbin presently taking up the traveling wire is automatically changed over to the empty bobbin.
Next, referring to FIGS. 3 and 4, an automatic changeover operation is explained. FIG. 3 shows a condition before the changeover operation is carried out. FIG. 4 shows a condition while the changeover operation is progressing. In FIG. 3, reference numerals 10, 11 denote bobbin holders having snaggers 10a, 11a. A reference numeral 12 denotes a presently take-up bobbin installed on the bobbin holder 10. A reference numeral 13 denotes an empty bobbin installed on the bobbin holder 11. A reference numeral 14 denotes a traverser, and a reference numeral 15 denotes a main wire shifting guide 15. Reference numerals 16, 17 denote sub wire shifting guides. Shortly before a take-up length of the presently take-up bobbin 12 reaches a predetermined value, the empty bobbin 13 is caused to rotate at a speed synchronous with the take-up speed of the presently take-up bobbin 12.
And further, in the before-changeover condition of FIG. 3, the traverser 14 shifts in a traverse direction toward a position indicated in the drawing and stops at an end in a widthwise direction. Then, the traveling wire 9 is continuously taken up in the presently take-up bobbin 12 in the condition where the traveling wire 9 contacts with the empty bobbin 13.
And, in the changeover condition of FIG. 4 wherein the winding thickness in the bobbin 12 has reached a predetermined value, the main wire shifting guide 15 and the sub wire shifting guide 16 advance to the positions shown in the drawing. The traveling wire 9 is hooked by the snagger 11a at the portion indicated by the number (1) so that an automatic changeover to the empty bobbin 13 can be accomplished. To the contrary, the traveling wire 9 is spaced far from the snagger 10a at the portion indicated by the number (2).
However, in above traveling wire take-up method explained with reference to FIG. 4 in which the wire shifting levers 15, 16, and 17 are used, a tension of the traveling wire varies due to friction. For example, in the case where the apparatus is driven with a take-up tension of 1 Kg in the before-changeover condition of FIG. 4, the take-up tension of the traveling wire 9 increases, for example, 1.3 Kg at the position (2). To the contrary, the take-up tension of the traveling wire 9 decreases, for example, 0.7 Kg at the position (1).
Therefore, a force for tearing off the traveling wire by the snagger 11a becomes weak, thereby increasing probability of changeover failure. Namely, this phenomenon is the same as the case that the wire is cut by scissors, wherein cutting operation becomes harder as tension force becomes smaller. If changeover failure occurs, not only a large amount of inferior wires are generated but approximately one hour is required to resume the normal condition. As a result, the working rate of the wire coating line is greatly reduced.